1. Field of the Invention
The present invention relates to an aqueous fluorescent ink for ink jet recording, where recording is carried out by discharging ink droplets using thermal energy. The present invention also relates to an ink cartridge, a recording unit, an ink jet recording apparatus, and an ink jet recording method using this ink.
2. Related Background Art
Fluorescent coloring materials have been used for line markers etc., and recently, inks using fluorescent pigments for improved durability have appeared. For example, Japanese Patent Application Laid-Open Nos. 6-346013 and 5-239395 disclose fluorescent pigment inks using organic fluorescent pigments for writing utensils.
In addition to the above-described use, fluorescent ink has been used for printing watermarks, indicia and the like.
Japanese Patent Application Laid-Open No. 9-291246 discloses application of an ink jet printer for such printing, where the water-proof ink composition using a soluble toner contains a nonionic surfactant having an H. L. B. (Hydrophile Lipophile Balance) of 8 to 15 as a solubilizing agent.
If the fluorescent intensity of a printed watermark or indicia is utilized as a threshold value, stable fluorescence emission is important. However, stable fluorescence intensity is not always obtained with the above-described prior arts.
Further, in the ink jet recording system utilizing thermal energy for ink ejection (so-called bubble jet system), steady bubble formation is required for steady ink ejection. The above-described inks are not satisfactory from such a point of view.
An object of the present invention is to provide an aqueous fluorescent ink capable of emitting stable fluorescence and excellent in ink discharging properties for ink jet recording, especially for bubble-jet recording, and further to provide a recording unit, an ink cartridge, an ink jet recording apparatus, and an ink jet recording method that can stably form images of high quality and durability owing to the excellent ejection properties of the ink.
The above-described purpose can be achieved as follows.
According to one aspect of the present invention, there is provided an aqueous fluorescent ink for ink jet recording that comprises: an emulsified resin colored with a fluorescent dye, and a water-soluble compound being solid at 25xc2x0 C. and having ethylene oxide units.
In the above-described ink, the emulsified resin is preferably an emulsified acrylic resin polymer.
According to still another aspect of the present invention, there is provided a recording unit that comprises an ink container storing an aqueous fluorescent ink described above and an ink jet head for discharging the ink.
According to still another aspect of the present invention, there is provided an ink cartridge storing an aqueous fluorescent ink described above.
According to still another aspect of the present invention, there is provided an ink jet recording apparatus that comprises an ink container storing an aqueous fluorescent ink described above.
According to still another aspect of the present invention, there is provided an ink jet recording method that comprises the step of discharging an aqueous fluorescent ink described above by an ink jet method.